Minderella, While I'm not wild about using perlite (for the same reasons Mel avoids it--rock hard and floats), it will aerate the soil, although it doesn't hold moisture as well as vermiculite.

What size vermiculite are you using? I discovered that our area HDepot had a type that was quite fine (which I used in my first batch), while a medium grade is what is recommended. I had to search a bit to find it, and am glad I did, because it makes a big difference in how loose my mix is. The manufacturer was the same for each size, which was not specified on the outside--I actually had to feel through the plastic bag to determine if it was chunky enough.

Some settling after a few waterings is normal, more so with the finer vermiculite. A little fluffing up with a trowel or your fingers can help restore some friability of the mix in an empty square, or gently around seedlings.

Minderella - I'd suggest you also add more compost as summer weather decomposes what compost is in the mix pretty quickly. The compost you had has broken down.

Our daughter added perlite this spring to stop the puddling in her boxed soil she acquired from someone else. I suppose eventually it works it's way up & she might have to turn the entire box when not cropping. For now the garden is productive with it.